This invention relates to a method for the manufacture of an ion-exchange membrane by the graft polymerization of an alkali salt or alkaline earth salt of an .alpha.-alkyl acrylate onto a hydrophilic polymer.
It has heretofore been known in the art to manufacture a graft polymer membrane by graft polymerizing a monomer on a polymer film through the application of high-energy or ultraviolet radiation or through the use of a catalyst, either after the monomer has been or while it is being adsorbed on the polymer film.
Where the combination of the monomer and the polymer involved happens to be such that the monomer is incapable of adsorption on the polymer, the graft polymer cannot be obtained by this conventional method. For example, solid monomers such as the alkali salts of .alpha.-alkyl acrylates are hardly adsorbed by cellulosic and hydrophilic polymers or by polyolefins. None of the combinations of these monomers and polymers, therefore, are capable of producing graft polymers by the aforementioned conventional method of graft polymerization. There has also existed a practicable method for manufacturing a graft polymer by dissolving a solid monomer in an organic solvent such as, for example, methanol or benzene, then soaking a polyolefinic or cellulosic polymer in the resultant solution and causing the monomer to be graft polymerized onto the polymer by virtue of a ionizing high-energy or ultraviolet radiation or a catalyst. This method, however, entails extra treatments for the removal of the unaltered monomer and the solvent which have impregnated the graft polymer and for the disposal of the by-produced polymer and the residual solvent occurring in the reaction. Moreover, the film to be manufactured by this method is swelled and possessed of uneven surfaces. For the purpose of commercial application, therefore, this method proves to be disadvantageous.
The object of this invention is to provide a method for manufacturing an ion-exchange graft polymer by graft polymerizing an alkali salt or alkaline earth salt of an .alpha.-alkyl acrylate onto a hydrophilic polymer incapable of ion exchange and onto which said salt is not adsorbable, without use of an organic solvent.